Book review: Discovery of Oyu Tolgoi: A case study of mineral and geological exploration
No abstract available.
Economic Geology↗
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The US Geological Survey’s Earth Mapping Resources Initiative (Earth MRI)—Providing framework geologic, geophysical, and elevation data to the nation’s critical mineral-bearing regions
New detailed mapping of the geologic resources of the Nation has the potential to significantly close the gap in the essential data needed to fuel a modern era of economic development and technological innovation, while at the same time dramatically enhancing our understanding of the fundamental way geology impacts everyday life, from the domestic critical mineral resources that are necessary for modern technology and the economy, to domestic energy and water resources, geologic hazards, agriculture, and other pressing needs. The U.S. Geological Survey established the Earth Resources Mapping Initiative (Earth MRI) to address the shortfall in geologic, geophysical, and elevation data with sufficient detail to support evaluation of regions in the United States that have potential to host critical mineral resources. The new effort is a collaboration with the Association of American State Geologists, who are providing new detailed geologic maps and making available online archived data and information related to critical mineral resources. The geophysical and lidar surveys are being contracted through industry specialists to assure that high-quality data are available to the public. This article provides an overview of the Earth MRI effort with discussions on the initial geophysical surveys funded for areas that have known potential for rare earth element resources. Subsequent projects are being designed to address areas that may host other critical mineral resources.
Fast Times↗
Tungsten skarn mineral resource assessment of the Great Basin region of western Nevada and eastern California
A new quantitative mineral resource assessment for tungsten, a critical mineral commodity with highly concentrated production and a moderate risk of global supply disruption, was conducted for the Great Basin region of western Nevada and eastern California. This assessment was part of a larger effort focusing on three regions in the United States and represents the first study of domestic tungsten resources and mineral potential in over twenty years. By integrating geology, bedrock and stream sediment geochemistry, geophysics, and remote sensing data with recently developed software tools and analyses, estimates of undiscovered tungsten skarn deposits in permissive tracts are combined with grade and tonnage distributions of known deposits to generate probabilistic estimates of undiscovered resources. Identified resources in the Great Basin region total 168 thousand metric tons (kt) of tungsten trioxide (WO 3 ), including 116 kt of past production and 52 kt remaining in place. Consistent with the historic significance of the Great Basin region as a past producer containing a large portion of U.S. identified resources, undiscovered resources are likely to occur adjacent to known deposits and prospects and at unexplored depths. Undiscovered deposits are estimated to contain median resources of 940 kt of WO 3 with a 90% probability of at least 420 kt and a 10% probability of at least 1.7 million metric tons (Mt), of which 240 kt to 1.1 Mt may be economic to extract. Based on a 20-year average price, median recoverable undiscovered resources are estimated at 570 kt WO 3 equivalent with a net present value of $3 billion U.S. dollars. The methods, data, results, and economic significance of the assessment contribute to a scientific understanding of a critical mineral resource with direct implications for policy and land management decisions.
California, Nevada↗
Structure mapping on enhanced landsat images of Southern Brazil: Tectonic control of mineralization and speculations on metallogeny
Computer enhancement, particularly contrast-stretching, reveals a previously unnoticed east-west structural zone across a Landsat image of the southern Brazilian Precambrian shield. In this zone occur the only known economic or near-economic deposits of gold, tin, and copper. Such deposits are typically localized by small east-west structural elements. Non-economic copper occurrences elsewhere in the region appear to be related to major northeast- and northwest-trending lineaments mapped on Landsat images. Mineral exploration should be primarily directed at the main east-west lineament, but two other possible east-west zones might be worthwhile targets also. The major east-west lineament projects through a break in the continental shelf, across the Atlantic along a large transoceanic fracture zone and into the African continent along a mapped tectonic trend that goes through an area that produces copper, gold, and tin. Global geophysical data suggest that the mapped east-west trend in South America is a surface reflection of structures that developed in the tectosphere in Precambrian time and that have persisted until the present. © 1977 Society of Exploration Geophysicists.
Geophysics↗
Environment of ore deposition in the Creede mining district, San Juan Mountains, Colorado: Part VI. Maximum duration for mineralization of the OH vein
The rate at which ore deposits form is one of the least well established parameters in all of economic geology. However, increased detail in sampling, improved technology of dating, and sophistication in modeling are reducing the uncertainties and establishing that ore formation, at least for the porphyry copper-skarn-epithermal base and precious metals deposit package, may take place in surprisingly brief intervals. This contribution applies another approach to examine the duration of mineralization. The degree to which compositional gradients within single crystals has flattened through solid-state diffusion offers a measure of the thermal dose (that is temperature combined with time) that the crystals have been subjected to since deposition. Here we examine the steepness of gradients in iron content within individual single sphalerite crystals from the epithermal silver-lead-zinc deposit in the OH vein at Creede, Colorado. Two initial textures are considered: growth-banded crystals and compositionally contrasting overgrowths that succeed crosscutting dissolution or fractured surfaces. The model used estimates the maximum possible time by assuming a perfectly sharp original compositional step, and it asks how long it would take at a known temperature for the gradient measured today to have formed. Applying the experimentally determined diffusion rates of Mizuta (1988a) to compositional gradients (ranging from 0.4-2.2 mol % FeS/??m) measured by the electron microprobe in 2-??m steps on banded sphalerite formed early in the paragenetic history yields a maximum duration of less than ???10,000 yr. Sphalerite from a solution unconformity in a position midway through the paragenetic sequence is indistinguishable from instantaneous deposition, supporting the conclusion of rapid ore formation. While this formation interval seems very brief, it is consistent with less well constrained estimates using entirely different criteria. ?? 2005 Society of Economic Geologists, Inc.
Economic Geology↗
Heavy mineral sands resources in China
About 200 known coastal deposits of heavy mineral sands (HMS) occur in China, in which considerable mineral resources of titanium, zircon, rare earth elements, and thorium exist in the forms of ilmenite, rutile, zircon, and monazite. More than 20 of these HMS deposits are reported as having been or are actively being mined in China during the past three decades, of which 12 have been reported to have industrial resources. Commercially important deposits occur almost entirely in Cenozoic beach and sand dune deposits, principally along China’s eastern coast (e.g., Shandong Province) and southern coast (e.g., Guangxi, Guangdong, Hainan, and Fujian provinces), and particularly on Hainan island. There are also important deposits of HMS along coastal areas of Taiwan. China has the largest share of the world’s economic ilmenite resources in HMS deposits (31%). A variety of igneous and associated metamorphic rocks along the coastal areas of China provided an abundant source of heavy minerals for the formation of the HMS occurrences. Studies of titanium-rich HMS deposits have shown that ilmenite is mostly sourced from igneous rocks. For example, 40% of the bedrock of Hainan island consists of Triassic and Cretaceous granites emplaced into rocks of the Cathyasia Block, and all of the HMS districts on the island lie no more than 15 km downstream from a Middle Triassic suite of syenite to granite intrusions. The southern coastal regions of Guangdong and Guangxi provinces are dominated by Jurassic granodiorite, biotite granite, two-mica granite, and A-type granite, with minor gabbro and syenite. Identified accessory minerals in the Jurassic alkaline granitoids include zircon, apatite, allanite, titanite, magnetite, ilmenite, monazite, and niobite. Thus, multiple plutons are in proximity to the Cenozoic coastal plain and are available as bedrock sources for the detrital titanium minerals, zircon, and monazite. More than 100 HMS deposits and prospects have been identified in Shandong Province, consisting of more than 20 varieties of heavy minerals in quartz sand, which include zircon, ilmenite, rutile, monazite, magnetite, xenotime, and gold (in general order of abundance) derived from Precambrian metamorphic basement and Mesozoic intrusions. Of these minerals, zircon, magnetite, gold, and quartz sand have economic significance. The quartz sands are used by the glass and construction industries. The placers mainly occur in and adjacent to the littoral zones of the northern and southern coasts of the Jiaodong Peninsula in Shandong province. Seven beach placer, HMS prospective areas have been delineated in coastal areas of the peninsula. Due to nearly exhausted placer reserves in the Chinese coastal zones, as well as increased environmental restrictions, future prospecting for heavy minerals will likely focus on ancient beach systems in China’s inland sedimentary basins. Also, offshore deposits of HMS in shallow coastal waters are other potential sources of heavy minerals, such as the Baoding Sea zircon-titanium, minerals-rich placer under development near Wanning on Hainan. Similarly, there is potential for offshore HMS deposits in shallow waters of the entire coastal area of southern Taiwan that remains to be fully evaluated. Reconnaissance sampling along Taiwan island’s coasts has revealed the potential for extensive, high-grade HMS accumulations nearshore.
Book chapter↗
Economics of mining law
Modern mining law, by facilitating socially and environmentally acceptable exploration, development, and production of mineral materials, helps secure the benefits of mineral production while minimizing environmental harm and accounting for increasing land-use competition. Mining investments are sunk costs, irreversibly tied to a particular mineral site, and require many years to recoup. Providing security of tenure is the most critical element of a practical mining law. Governments owning mineral rights have a conflict of interest between their roles as a profit-maximizing landowner and as a guardian of public welfare. As a monopoly supplier, governments have considerable power to manipulate mineral-rights markets. To avoid monopoly rent-seeking by governments, a competitive market for government-owned mineral rights must be created by artifice. What mining firms will pay for mineral rights depends on expected exploration success and extraction costs. Landowners and mining firms will negotlate respective shares of anticipated differential rents, usually allowing for some form of risk sharing. Private landowners do not normally account for external benefits or costs of minerals use. Government ownership of mineral rights allows for direct accounting of social prices for mineral-bearing lands and external costs. An equitable and efficient method is to charge an appropriate reservation price for surface land use, net of the value of land after reclamation, and to recover all or part of differential rents through a flat income or resource-rent tax. The traditional royalty on gross value of production, essentially a regressive income tax, cannot recover as much rent as a flat income tax, causes arbitrary mineral-reserve sterilization, and creates a bias toward development on the extensive margin where marginal environmental costs are higher. Mitigating environmental costs and resolving land-use conflicts require local evaluation and planning. National oversight ensures that the relative global avaliability of minerals and other values are considered, and can also promote adaptive efficiency by publicizing creative local solutions, providing technical support, and funding useful research. ?? 1995 Oxford University Press.
Nonrenewable Resources↗
Earth and water resources and hazards in Central America
Long-range economic development in Central America will depend in large part on production of indigenous mineral, energy, and water resources and on mitigation of the disastrous effects of geologic and hydrologic hazards such as landslides, earthquakes, volcanic eruptions, and floods. The region has six world-class metal mines at present as well as additional evidence of widespread mineralization. Systematic investigations using modern mineral exploration techniques should reveal more mineral deposits suitable for development. Widespread evidence of lignite and geothermal resources suggests that intensive studies could identify producible energy sources in most Central American countries. Water supply and water quality vary greatly from country to country. Local problems of ground- and surface-water availability and of contamination create a need for systematic programs to provide better hydrologic data, capital improvements, and management. Disastrous earthquakes have destroyed or severely damaged many cities in Central America. Volcanic eruptions, landslides, mudflows, and floods have devastated most of the Pacific side of Central America at one time or another. A regional approach to earthquake, volcano, and flood-risk analysis and monitoring, using modern technology and concepts, would provide the facilities and means for acquiring knowledge necessary to reduce future losses. All Central American countries need to strengthen institutions and programs dealing with earth and water resources and natural hazards. Some of these needs may be satisfied through existing or pending projects and technical and economic assistance from U.S. or other sources. The need for a comprehensive study of the natural resources of Central America and the requirements for their development is evident. The U.S. Caribbean Basin Initiative offers both an excellent opportunity for a regional approach to these pervasive problems and an opportunity for international cooperation.
Circular↗
Monazite in Atlantic shore-line features
This report is a survey of present and potential production of monazite from part of the Maryland-Florida section of the Atlantic Coastal Plain. The part of the Coastal Plain covered here is the outer (shore-ward) half. In this area, all the large heavy-mineral placers so far discovered occur in sand bodies that, by their shape, size, orientation, and lithology, appear to be ancient beaches, spits, bars, or dunes. Smaller placers have produced from recent shore-line features. The inner part of the Coastal Plain, to be treated in another report, is underlain generally by older rocks, ranging in age from Cretaceous to older Pleistocene. Only two large heavy-mineral placers are now in production at Trail Ridge, and near Jacksonville, both in Florida. Production is planned for the near future near Yulee, Fla.: in Folkston, Ga.: and at one or two localities in eastern North Carolina. Each of these three will produce monazite as a byproduct; the total new reserve for the three placers is about 33,000 tons of monazite. In large heavy-mineral placers of this type, monazite has not been found to run more than about 1 percent of total heavy minerals. In some large placers, notably Trail Ridge, it is almost or completely lacking. No reason for its sporadic occurrence has been found in this investigation. Two placers of potential economic value have been found by this project in Virginia, one west and one east of Chesapeake Bay. Neither is of promise for monazite production, but if they serve to open up exploration or production in the area, there is a chance for monazite as a byproduct from other placers. A discovery of considerable scientific interest has to do with the occurrence of two different suites of heavy minerals in the Coastal Plain, at least south of Virginia. One, an “older” suite, lacks epidote, hornblende, and garnet; this suite occurs in all older formations and in Pleistocene deposits lying above about 50 or 60 feet above sea level. The other, “younger” suite contains these three minerals: it is restricted to recent beaches and streams, and to Pleistocene deposits at low altitudes. Monazite may occur with either of these suites. The percentage of titania (TiO 2 ) in illmenite is of both scientific and economic interest. Illmenite is by far the most sought-for mineral in present exploration, and whether it contains the “normal” 53 percent of titania or, as it commonly does in Florida, 60 percent, is often of decisive importance in its exploitation. The nature, time, and place of this “enrichment” in titania has not been worked out. The heavy-mineral industry of the area seems to give promise of considerable expansion in the near future, and a greater monazite production seems assured.
Florida;Maryl;North Carolina;South Carolina;Virgin↗
Resource data bases-Resource assessment
The U.S. Geological Survey's Office of Resource Analysis is developing computer methods for the handling of mineral-resources data in order to provide improved means for addressing and manipulating data. These methods include: computerized data files and predictive resource models. Data files contain the raw or disaggregated information on mineral deposits and commodities. One operational data file is CRIB (Computerized Resources Information Bank) which is a general purpose inventory and reference file on metallic and nonmetallic mineral deposits. A computer file on resources should contain detailed information on the following main categories: record identification, name and location, description of deposit, analytical data, and production/reserves. A resource model employs postulates and inferences in conjunction with the data to make predictions about resources-as key variables concerning a mineral commodity are changed. The objective is to estimate the availability of minerals including: geological availability (occurrence models), technological availability (exploration and beneficiation models), and economic availability (economics models). ?? 1976.
Computers & Geosciences↗
The 3D Elevation Program—Supporting Montana’s economy
Introduction Montana, America’s fourth largest State with an area of 147,040 square miles, is defined by its diverse terrain. The western two-fifths of the State falls within the Rocky Mountains and the eastern three-fifths is in the Great Plains. Because of its location along the Continental Divide, the rivers in Montana drain into either the Pacific Ocean or the Gulf of Mexico. Montana is often called the Treasure State due to its mineral wealth, which includes oil, gas, and coal, but the State’s primary economic activity is agriculture. Other economic activities include natural resources conservation, water supply and quality, infrastructure and construction management, flood risk management, and geologic resource assessment and hazard mitigation. Critical applications that meet the State’s management needs depend on light detection and ranging (lidar) data that provide a highly detailed three-dimensional (3D) model of the Earth’s surface and aboveground features.
Montana↗
Atlas of water resources in the Black Hills area, South Dakota
The Black Hills area is an important resource center that provides an economic base for western South Dakota through tourism, agriculture, the timber industry, and mineral resources. In addition, water originating from the area is used for municipal, industrial, agricultural, and recreational purposes throughout much of western South Dakota. The Black Hills area also is an important recharge area for aquifers in the northern Great Plains. Population growth, resource development, and periodic droughts have the potential to affect the quantity, quality, and availability of water within the Black Hills area. Growth has resulted in competing interests for available water supplies. The Black Hills Hydrology Study was initiated in 1990 to address these concerns. This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators.
Hydrologic Atlas↗
U.S. Geological Survey offshore program of resource and geo-environmental studies and topical investigations, Pacific-Arctic region
The Geological Survey's marine geology investigations in the Pacific-Arctic area are presented in this report in the context of the underlying socio-economic problem of expanding the domestic production of oil and gas and other mineral and hard- and soft-rock resources while maintaining acceptable standards in the marine environment. The primary mission of the Survey 's Pacific-Arctic Branch of Marine Geology is to provide scientifically interpreted information about the (1) resource potential, (2) geo-environmental setting, and (3) overall geologic characteristics of the continental margins (that is, the continental shelf, slope and rise) and adjacent deeper water and shallower coastal areas off California, Oregon, Washington, Alaska and Hawaii and also, where it is of interest to the U.S. Government, more remote deep-sea areas of the Pacific-Arctic realm.
Open-File Report↗
Map showing areas with potential for talc deposits in the Gravelly, Greenhorn, and Ruby Ranges and the Henrys Lake Mountains of southwestern Montana
For the last several years, Montana has been the leading talc producing state in the United States (U.S. Geological Survey, 1996). For example, in 1992 Montana supplied about 40 percent of the U.S. mine production of talc (Virta, 1992). All of this production has come from the large deposits of high purity talc in the southwestern part of the state. All Montana talc is currently (1997) extracted from four mines, each within the study area of this map—the open pit operations of the Treasure State, Regal, and Yellowstone mines and the underground operation of the Beaverhead mine (see map numbers 1-4 on list and map to the left). The related mineral chlorite is mined at the Antler mine, located nearby, but outside of the study area in the Highland Mountains. Montana talc has at least two market advantages: (1) some deposits are very large and near surface, allowing economic mining by open pit methods; and (2) the deposits are of high purity and lack tremolite or other amphibole mineral contaminants (such as absestos) that occur in some other talc-rich deposits. Talc from southwest Montana is used in ceramics, paint, paper, plastics, cosmetics, rubber, roofing, flooring, caulking, and agricultural applications. The talc is also used in the processes of recycling paper and plastics. Talc was first discovered in the early 1900's at the present site of the Yellowstone mine (Perry, 1948, p. 9). Modest production began in 1942 from shallow pits and adits, supplying steatite (massive, compact, high-purity) talc that was used to make ceramic insulators. The southwest Montana talc industry grew to become a significant part of the region's economy; this history is described by Perry (1948), Olson (1976), and Berg (1997). Exploration and development are likely to continue for the foreseeable future for several reasons: (1) mines are active in the area at present and an infrastructure for talc processing exists; (2) large changes in domestic and export talc markets are not expected in the next few years based on recent market trends (Virta, 1997); (3) the talc of this region is especially pure and asbestos-free; and (4) except for potential ground stabilization problems and land disturbance associated with largescale open pit mining, no significant environmental impacts are associated with talc mining.
Montana↗
Sulfate minerals: Crystallography, geochemistry and environmental significance
No abstract available.
Economic Geology↗
Report, of committee on basic research in the field of. industrial minerals and rocks
No abstract available.
Economic Geology↗